CLEMSON, SC (CNN Newsource) — More than 200 unmarked graves of slaves have been found on the campus of Clemson University.

The school says the gravesites date back to the 1800s and the people buried there built the school.

The University is working to preserve the grounds.

Clemson University’s Woodland Cemetery sits in the shadows of Death Valley. Behind the memorial stadium sits a previously unknown burial site dating back to the 1800s.

“Now that we know that there are more burials here, we certainly have a responsibility for making sure that the people who helped build the university, the people whose labor kept the Fort Hill plantation going, we cannot, not honor them because we are indebted to Black labor for the existence of Clemson University,” said Rhondda Thomas, Calhoun Lemon Professor of Literature at Clemson.

The discovery came as Clemson University researchers were preparing to honor the graves in Fort Hill Slave and Convict Cemetery.

The University historian says that they used ground-penetrating radar or GPR which unearthed the hidden graves.

“In the midst of that process we began finding field stones which are the traditional markers of African American burials, and they were not just here in the fence, they extended all the way out to about three acres,” said Paul Anderson, Clemson University, Historian, Professor of History.

Anderson says the scan found more than 200 potential gravesites in the cemetery and additional graves believed to be underneath a walking path.

“We know we’re going to find more. The documentary records suggest oral history, which has as many as 250 African Americans buried here. Most of them are likely to be former slaves,” Anderson said.

The University says their top priority is finding a way to honor their lives and give a voice to the African Americans buried in the cemetery. It has hired a historian to lead the research and document what they find on those grounds.

All of their findings will be posted online.

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